The present invention relates generally to continuously supplying flexible raw material generally in the form of a web to a processing machine, and more particularly to a stock of ribbon material and methods for controlling twisting of the ribbon material fed to the processing machine.
Conventional processing machines, such as those used to convert narrow ribbons of raw material into finished product, run most efficiently when a continuous feed of raw material is provided. If continuous feed of raw material is not maintained, the machine must be shut down to re-thread the ribbon material. Shutting down the machine negatively impacts the efficiency of the machine, especially machines used in high volume processes such as the production of feminine care products.
Raw absorbent material used to produce feminine care products is initially manufactured as a web of absorbent material measuring one meter or more in width. The processing machine cannot process such a wide web, so the material is trimmed to form many ribbons of a more usable narrow width. The wide web is suitably scored or sheared to form the ribbons. Typically, the ribbons are then wound onto cores to form coils or xe2x80x9cpancake slitsxe2x80x9d, so-called due to the fact they resemble pancakes when laid flat. Each coil has a thickness substantially equal to a width of the ribbon material, and each successive revolution or turn of ribbon substantially overlies the preceding revolution so that the coil is no thicker than the ribbon material is wide.
The coils are shipped to a factory where the processing machine is located, and one coil at a time is mounted on a horizontal axis spindle for continuous feed of raw material into the processing machine. The machine pulls the ribbon in a direction tangential to the coil, i.e., parallel to a plane of the coil and perpendicular to an axis of the coil, so that there is no twisting of the ribbon during feeding. The spindle is a variable-speed motorized spindle with sufficient capacity for mounting only one coil of absorbent material. The spindle is variable-speed to keep tension in the ribbon as it is fed into the machine. It will be understood that at a constant linear feed rate, the coil will rotate faster as its supply of ribbon is consumed by the machine. Due to the high cost of each spindle, no more than two spindles are typically provided at the machine. Thus, as a first coil is consumed, a second coil is mounted on the second spindle, and the trailing end of the first coil is spliced to a leading end of the second coil.
An obvious disadvantage of this arrangement is that an operator must be standing by to load coils as they are consumed by the machine. The time period between changing coils (referred to as runout time) will vary with the length of the material on the coil and the speed of use by the processing machine. In the case of a relatively high throughput feminine pad machine, a typical one thousand lineal meter coil of absorbent material will be consumed in three to nine minutes. Due to this relatively short runout time, the processing machine requires constant manpower to maintain continuous feed. Moreover, the short runout time and the difficulty of loading the bulky coil on the spindle increases the likelihood that the splice will fail (e.g., due to operator error or mechanical problems in splicing) and the likelihood that the machine will have to be shutdown for re-threading.
There are other methods of providing continuous feed material to a processing machine. For example a processing machine is shown in U.S. Pat. No. 1,178,566 (Wright) wherein the ribbon material is formed into a stack of coils, and an end of the upper coil is pulled parallel to the axis of the coil into the machine. This arrangement causes the ribbon material to twist as it is unwound. The patent shows a device for removing the twists including a rotatable guide which rotates in response to twists in the ribbon and a powered turntable which intermittently rotates the coils (i.e., rotation starts and stops repeatedly) in response to rotation of the guide.
In one aspect, the present invention provides a method of controlling twisting in ribbon material fed from a coil of ribbon material into a processing machine. The coil has a central axis perpendicular to a plane of the coil. The method includes pulling ribbon material from the coil in a twist-promoting direction and continuously rotating the coil during the pulling step at a rotational speed selected so that a number of twists in the unwound ribbon is maintained below a predetermined number.
In another aspect, the present invention provides a method of controlling twisting in ribbon material fed from a coil of ribbon material into a processing machine. The coil has a central axis perpendicular to a plane of the coil. The method includes pulling ribbon material from the coil in a twist-promoting direction and continuously rotating the coil during the pulling step at a rotational speed selected such that the number of twists in the unwound ribbon is maintained sufficiently low so that the material is substantially untwisted at a downstream portion of an intake feed mechanism of the processing machine.
In yet another aspect, the present invention provides a feed system of a processing machine for continuously feeding a coil of ribbon material thereto. The system includes an intake feed mechanism for pulling the ribbon material into the processing machine. The intake feed mechanism is adapted to pull the ribbon material from the coil in a twist-promoting direction. A powered turntable is positioned upstream from the intake feed mechanism for supporting the coil. The turntable continuously turns while the intake feed mechanism pulls the ribbon material into the processing machine.
In still another aspect, the present invention provides a feed system of a processing machine for continuously feeding ribbon material thereto. The system includes a turntable and a coil of the ribbon material mounted on the turntable. The coil has a central axis perpendicular to a plane of the coil. The system further includes means for pulling the ribbon material from the coil into the processing machine. The pulling means are adapted to pull the ribbon material from the coil in a twist-promoting direction. The system also includes means for continuously rotating the turntable and coil so as to reduce twisting in unwound ribbon material.
Other features of the present invention will be in part apparent and in part pointed out hereinafter.